Semiconductor devices including semiconductor substrate and wiring board have been enhanced their performances in pursuit of higher degrees of integration and micronization. Manufacturing processes for such semiconductor devices have adopted so-called chemical mechanical polishing (CMP), which has become indispensable typically for forming a shallow trench isolation, planarizing an insulation interlayer, and forming a contact plug or Cu damascene interconnect.
The CMP abrasive is typically composed of an abrasive grain and a chemical component, wherein the chemical component plays a role of promoting polishing through oxidation or corrosion of a film to be polished. Meanwhile, the abrasive grain plays a role of polishing based on mechanical action, for which the colloidal silica, fumed silica, or ceria particle is used. In particular, the ceria particle, capable of demonstrating a specifically high polishing rate on a silicon oxide film, has been applied to polishing in the shallow trench isolation process.
In the shallow trench isolation process, not only the silicon oxide film, but also silicon nitride film is polished. For easy isolation, the polishing rate of the silicon oxide film is preferably higher, and the polishing rate of the silicon nitride film is preferably lower, wherein the ratio of these polishing rates (selectivity) is also important.
In one conventional method of polishing these members, relatively coarse primary polishing is followed by fine secondary polishing, to thereby obtain a smooth surface or an extremely precise surface with less scratches or other flaws.
In relation to the abrasive used for the secondary polishing as this sort of finish polishing, the methods below have typically been proposed.
For example, Patent Literature 1 describes a method of manufacturing a ultrafine cerium oxide particle (average particle size=10 to 80 nm) composed of cerium oxide single crystal, obtained by mixing an aqueous cerium(III) nitrate solution and a base according to a quantity ratio capable of adjusting pH to 5 to 10, rapidly heating the mixture up to 70 to 100° C., and ripening the mixture at that temperature. The literature also describes that the manufacturing method can provide the ultrafine cerium oxide particle with high levels of particle size uniformity and particle shape uniformity.
Non-Patent Literature 1 discloses a method of manufacturing ceria-coated silica, containing a manufacturing process similar to the method of manufacturing the ultrafine cerium oxide particle described in Patent Literature 1. The method of manufacturing ceria-coated silica does not have calcination and dispersion processes which were contained in the method of manufacturing described in Patent Literature 1.
Patent Literature 2 describes a silica-based composite particle that includes amorphous silica particle A, having thereon crystalline oxide layer B that contains one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum and strontium. The literature also describes, as one preferred embodiment, a silica-based composite particle that includes amorphous silica particle A; having on the surface thereof oxide layer C that is an amorphous oxide layer but different from the amorphous silica layer, and containing aluminum or other element; and having further thereon crystalline oxide layer B that contains one or more elements selected from zirconium, titanium, iron, manganese, zinc, cerium, yttrium, calcium, magnesium, fluorine, lanthanum and strontium. According to the description, with the crystalline oxide layer B provided to the surface of amorphous silica particle A, the silica-based composite particle can improve the polishing rate; pretreatment of the silica particle contributes to suppress the particles from being sintered during calcination, and to improve the dispersibility in a polishing slurry; and absence or largely reduced amount of consumption of cerium oxide enables provision of an abrasive with a high polishing performance at low cost. It is also described that, the composite particle, having such additional amorphous oxide layer C between silica-based particle A and oxide layer B, shows particularly strong effects of suppressing sintering of particles and of improving the polishing rate.